Igneous Petrogenesis Study And Ore-forming Process Of Qiaohuote Copper, Xinjiang

Qiaohuote copper deposit has suitable porphyry copper metallogenic geologicaltectonic environment which is located between South Tianshan Suture Zone andNorthern Nalati Fault Belt. Based on a systemic research on igneous petrology,petrography, geochemistry, zircon U-Pb chronology and Sr-Nd isotope in this paper,and combined with others’ data in this deposit, we can demonstrate igneouspetrogenesis and geotectonic environment in this district, discuss the relationshipbetween magmatite and the ore deposit, limited the start time of ancient SouthTianshan Ocean northword subduction. Through the research in this paper, we haveobtained the following understanding:1, The volcanic rocks are mostly basalts, basaltic andesites and andesites, a few daciteand rhyolite. The geochemical characteristics show enrichment in LILE and depletionin HFSE, especially obvious Nb, Ta, Ti, P negative anomalies. It is similar to theHusdon volcanic rocks. Combine with regional geological, therefore, indicated thatthe volcanic rocks are active continental margin arc rocks.2, Zircon LA-ICP-MS U-Pb chronology show that, basaltic andesite, dacite,granodiorite, orthophyre obtain ages of455.6±8.1Ma,444.5±1.9Ma,455.4±5.3Ma,441.4±1.6Ma, respctively. Which show that ancient South Tianshan Ocean northwordsubduction is earlier than late Ordovician, and that magmatite formed multipleperiods.3, Trace elements and REE normalized patterns, element ratioes, and+εNd(t) valuesproved that the magma is derived from depleted mantle modified by subductionmetasomatic fluids. Andesite, dacite, rhyolite, granodiorite, orthophyre have similartrace elements and REE normalized pattern and Sr-Nd isotope values to basalt,basaltic andesite, suggest that intermediate-acidic rocks derive from the evolution ofbasaltic magma.4, The emergence of bimodel volcanic rocks implied extention environment, becauseof the change of subduction angle. 5, Comprehensively we study and previous studies of fluid inclusions, H-O isotope,sulfer isotope, and compared with other typical porphyry coppers, suggests thatQiaohuote has all elements to be a porphyry copper. The lower fluid inclusionshomogenization temperature, salinity and formation pressure, indicated lowerdegradation of the copper. This copper deposit in surface is of the hydrothermal typedeposit, the porphyry copper deposit prospecting potential in deeper.